U.S. patent number 4,943,748 [Application Number 07/369,990] was granted by the patent office on 1990-07-24 for motor with cup-shaped rotor having cylindrical portions of different diameter.
This patent grant is currently assigned to Yugen Kaisha Chubuseimitsu. Invention is credited to Shinichi Shiozawa.
United States Patent |
4,943,748 |
Shiozawa |
July 24, 1990 |
Motor with cup-shaped rotor having cylindrical portions of
different diameter
Abstract
Motor structure having a shaft supported on a frame rotatably by
bearings, a core arranged outside of the shaft, a cup-shaped rotor
arranged outside of the core, and a magnet fitted to the rotor, the
rotor having a rotor body integrally incorporated with the
above-mentioned shaft, and the rotor body having an opened end part
from which a magnet mounting section is bulged out, whereby the
above-mentioned magnet is fitted to the magnet mounting section,
facing the shaft.
Inventors: |
Shiozawa; Shinichi (Komagane,
JP) |
Assignee: |
Yugen Kaisha Chubuseimitsu
(Nagano, JP)
|
Family
ID: |
16010186 |
Appl.
No.: |
07/369,990 |
Filed: |
June 22, 1989 |
Foreign Application Priority Data
|
|
|
|
|
Jul 16, 1988 [JP] |
|
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63-176245 |
|
Current U.S.
Class: |
310/67R; 310/268;
360/98.07; G9B/19.028 |
Current CPC
Class: |
G11B
19/2009 (20130101); H02K 5/1735 (20130101); H02K
5/1737 (20130101); H02K 21/22 (20130101); H02K
29/08 (20130101) |
Current International
Class: |
G11B
19/20 (20060101); H02K 29/08 (20060101); H02K
5/173 (20060101); H02K 21/22 (20060101); H02K
29/06 (20060101); H02K 021/24 (); G11B
005/012 () |
Field of
Search: |
;310/67R,156,261,268
;360/98.06,98.07 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wong; Peter S.
Assistant Examiner: Rebsch; D. L.
Attorney, Agent or Firm: Jordan and Hamburg
Claims
What I claim is:
1. A motor structure comprising a frame wall and a hollow holding
cylinder extending generally perpendicular from said frame wall, a
rotor shaft coaxially disposed in said hollow holding cylinder,
said rotor shaft having an axis of rotation which is vertically
disposed, bearing means mounted on said hollow holding cylinder for
rotatably supporting said rotor shaft, said holding cylinder having
an outer part, coil means mounted on said outer part of said
holding cylinder, a cup-shaped rotor means mounted on said rotor
shaft, said cup-shaped rotor means having an end wall, a first
cylindrical portion extending coaxially from said end wall, an
intermediate wall extending radially outwardly from said first
cylindrical portion, and a second cylindrical portion extending
axially from said intermediate wall such that said first
cylindrical portion has a diameter which is less than the diameter
of said second cylindrical portion, said coil means being generally
axially aligned with and being disposed radially inwardly of said
second cylindrical portion, said coil means having an outer
diameter greater than the diameter of said first cylindrical
portion such that said coil means generally underlies said first
cylindrical portion, and magnet means mounted on said second
cylindrical portion radially outwardly of said coil means.
2. A motor structure comprising a motor means having a frame wall
and a hollow holding cylinder extending generally perpendicular
from said frame wall, a rotor shaft coaxially disposed in said
hollow holding cylinder, bearing means mounted on said hollow
holding cylinder for rotatably supporting said rotor shaft, said
holding cylinder having an outer part, coil means mounted on said
outer part of said holding cylinder, a terminal board means
disposed on said frame wall between said coil means and said frame
wall, a cup-shaped rotor means mounted on said rotor shaft, said
cup-shaped rotor means having an end wall, a first cylindrical
portion extending coaxially from said end wall, an intermediate
wall extending radially outwardly from said first cylindrical
portion, and a second cylindrical portion extending axially from
said intermediate wall such that said first cylindrical portion has
a diameter which is less than the diameter of said second
cylindrical portion, said coil means being generally axially
aligned with and being disposed radially inwardly of said second
cylindrical portion, said coil means having an outer diameter
greater than the diameter of said first cylindrical portion such
that said coil means is generally axially superimposed relative to
said first cylindrical portion, and magnet means mounted on said
second cylindrical portion radially outwardly of said coil
means.
3. A motor structure according to claim 2, wherein said coil means
has an outer radial portion disposed between said intermediate wall
of said cup-shaped rotor means and said frame wall.
4. A motor structure according to claim 2, wherein said magnet
means is disposed between said intermediate wall of said cup-shaped
motor means and said frame wall.
5. A motor structure according to claim 2, wherein said end wall of
said cup-shaped rotor means has an outer radial end, said first
cylindrical portion extending axially from said outer radial end of
said end wall, said intermediate wall having an inner radial end
and an outer radial end, said first cylindrical portion extending
axially from said inner radial end of said intermediate wall, said
second cylindrical portion extending axially from said outer radial
end of said intermediate wall.
6. A motor structure according to claim 2, wherein said rotor shaft
has an axis, said intermediate wall being perpendicular to said
rotor shaft axis, said first and second cylindrical portions being
coaxial with said rotor shaft axis.
7. A motor structure according to claim 2, wherein said rotor shaft
is joined to said end wall of said cup-shaped rotor means.
8. A motor structure according to claim 2, wherein said motor
structure is a disc drive motor for driving discs which are mounted
on said first cylindrical portion of said cup-shaped rotor
means.
9. A motor structure according to claim 2, wherein said rotor shaft
has a vertical axis, said first cylindrical portion overlying said
coil means.
10. A motor structure according to claim 9, wherein said first
cylindrical portion overlies said coil means.
11. A motor structure according to claim 9, wherein said
intermediate wall overlies said magnet means.
12. A motor structure according to claim 9, wherein said terminal
board means underlies said coil means.
13. A motor structure according to claim 2, wherein said rotor
shaft has a vertical axis, said coil means having an outer radial
portion, an intermediate radial portion and an inner radial
portion, said outer radial portion underlying said intermediate
wall, said intermediate radial portion underlying said first
cylindrical portion of said rotor means, said inner radial portion
underlying said end wall of said rotor means.
14. A motor structure according to claim 2, wherein said first
cylindrical portion of said rotor means has an inner and outer
cylindrical surfaces, said inner and outer cylindrical surfaces
each having a diameter less than the diameter of said coil means.
Description
FIELD OF THE INVENTION AND STATEMENT OF THE RELATED ART
The present invention relates to a motor structure used in a disc
drive motor or the like, for a magnetic recording apparatus or an
optical recording apparatus.
FIG. 2 shows an example of a disc drive motor which has been
already known. In this motor, the base part of a disc mounting
section 241 in a cup-shaped rotor 24 made of magnetic material is
rotatably fitted through a bearing 23 on the upper part of a shaft
22 which is planted upright on a frame 21 integrally therewith, and
further a flange-like disc abutting part 242 is formed on the outer
periphery of the lower end of the disc mounting section 241.
Further, a drive coil 26 is wound around a core 25 fitted on the
shaft 22 within the disc mounting section 241, and a magnet 27 is
fitted on the inner peripheral surface of the disc mounting section
241 outside of and adjacent to the coil. Further, in FIG. 2, there
are shown a disc 28 mounted on the disc mounting section 241, a
sensor 29 and a terminal board 30.
With the motor having the above-mentioned structure, since the
rotor 24 is fitted on the shaft 22, indirectly through the bearing
23, that is, it does not make contact with the shaft, static
electricity produced in the disc mounting section 241 cannot be
discharged, and accordingly, a high voltage is induced between the
disc mounting section and the shaft, causing electric erosion in
the raceway surface of the bearing 23, resulting in excessive shaft
deflection resulting in a problem of generation of noise. Further,
since the magnet 27 is fitted directly on the disc mounting
section, the rotor should be made of magnetic materials, and
accordingly, a difficult cutting process must be used for remedying
shaft deflection because a correcting process in which the outer
surface of an attaching surface or an abutting part is ground in
order to reduce shaft deflection after the assembly of the motor so
as to decrease the deflection of the disc mounting section 241 and
the abutting part 242 in the motor, is difficult if the rotor made
of magnetic materials is used.
Further, if the rotor is made of magnetic materials, rust
preventing treatment should be taken. After a correcting process
for decreasing the deflection, the rust preventing treatment should
be repeated for the thus processed or ground parts, and such a
correcting process is therefore cumbersome.
For example, Japanese Laid-Open Patent Nos. 61-112544 and 63-107438
disclose motors solving the above-mentioned problems. These motors
have substantially the same structure, and therefore, the motor
disclosed in Japanese Laid-Open Patent No. 63-107438 alone will be
explained briefly. As shown in FIG. 3, a shaft 32 is rotatably
fitted through the intermediary of bearings 33 in the center axial
part of a holding cylinder 311 planted upright on a motor frame 31,
and the base part of a disc mounting section 341 of a cut-shaped
rotor 34 having its lower end opened, is fitted on the upper end
part of the shaft which is projected from the holding cylinder,
integrally therewith. Further, a drive coil 36 is wound on a core
35 fitted on the outer peripheral part of the holding cylinder 311,
and a magnet 37 is fitted in the inner peripheral surface of a disc
mounting section 341 through the intermediary of a magnet yoke 41
outside of the core with a gap therebetween. Further, in FIG. 3
there are shown a sensor 39 and a terminal board 40.
In this example of the motor, since the rotor makes contact with
the shaft, it is possible to solve the first mentioned disadvantage
caused by static electricity inherent to the motor. However, since
the bearings are located inside of the core surrounded by the disc
mounting section, the diametrical dimensions of the bearings are
inevitably small, and accordingly, there is a disadvantage such
that detrimental effects are imposed upon the use life, impact
resistance and vibration resistance of the bearing. Further, since
the magnet is fitted in the inside of the disc mounting section,
the diametrical dimension of the magnetic are also inevitably
small, and accordingly, there is a further disadvantage such that
detrimental effects are imposed upon the characteristics of the
motor, such as the motor generation torque characteristic and the
like.
OBJECT AND SUMMARY OF THE INVENTION
An object of the present invention is to enable a shaft to be
supported by use of a large bearing.
Another object of the present invention is to ensure a long use
life, a high wear resistance and a high impact resistance for
bearings. Further object of the present invention is to propose a
motor structure which can use a magnet having large diametrical
dimensions. Moreover, further object of the present invention is to
enhance the characteristics of a motor such as the motor generation
torque characteristic.
According to the present invention, there is provided a motor
structure including a frame, a shaft a bearing rotatably supporting
the shaft in the frame, a core arranged outside of the shaft, a
rotor having one end opened and arranged outside of the rotor, and
a magnet fitted inside of a magnet mounting section formed in the
rotor. The rotor body of the above-mentioned rotor is mounted on
the above-mentioned shaft in a unit structure, and the
above-mentioned magnet mounting section is bulged out from the
opened end of the rotor body while the above-mentioned magnet is
fitted inside of the magnet mounting section, facing the
above-mentioned shaft.
The features of the present invention will become more apparent
when the present invention is explained with reference to the
drawings which are:
BRIEF DESCRIPTION OF THE DRAWINGS:
FIG. 1 is a cross-sectional view illustrating one embodiment of the
present invention; and
FIGS. 2 and 3 are cross-sectional views illustrating already
proposed motors relevant to the present invention,
respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
The present invention will be hereinbelow detailed in an embodiment
form which is applied on a drive motor structure in a disc
recording apparatus with reference to FIG. 1.
A holding cylinder 2 is planted upright on a motor frame 1,
integrally therewith. A shaft 3 is fitted rotatably in bearings 4
in a center axial part inside of the holding cylinder 2, the upper
end part of the shaft being projected upward from the holding
cylinder 2. The base part of a disc mounting section 51
constituting the body of a cup-shaped rotor 5 is fitted on the
upper end part of the shaft 3 integrally therewith. The rotor 5 has
an opened part facing downward. The lower end part of the disc
mounting section 51 is bulged out so as to form a magnet mounting
section 52 having an L-like cross-sectioned shape, and a magnet 6
is fitted in the inner peripheral surface of the magnet mounting
section 52 through the intermediary of a magnet yoke 7, facing the
shaft 3.
Further, a core 8 is fitted on the outer peripheral part of the
above-mentioned holding cylinder 2, and a drive coil 9 is wound on
the core 8, facing, at its outside, the above-mentioned magnet 6
with a gap therebetween.
Further, in FIG. 1, there are shown discs 10 mounted on the disc
mounting section 51 of the rotor, a sensor 11 and a terminal board
12.
In view of the foregoing arrangement according to the present
invention, since the magnet mounting section 52 is bulged out
outside of the rotor body 51 while the core 8 and the bearings are
disposed in the space surrounded by the magnet mounting section 52,
it is possible to use large size bearings, and accordingly, it is
possible to ensure a long use life, a high wear-resistance and a
high impact resistance for the bearings. Further, since the magnet
6 is mounted in the magnet mounting section 52, facing the shaft 3,
a magnet having large diametrical dimensions can be used, and
accordingly, it is possible to enhance the motor characteristics
such as a motor generation torque characteristic.
In the above-mentioned embodiment, since the magnet 6 is mounted in
the magnet mounting section 52 through the intermediary of the
magnet yoke 7, there is an advantage such that a material having a
suitable machinability can be selected for the rotor. It is natural
that the magnet 6 may be fitted directly in the rotor 5 with no
attaching member 7 therebetween. However, in this case, the rotor
should be made of magnetic materials.
The applicable field of the present invention should be limited to
the above-mentioned disc drive motor.
* * * * *